1. Field of the Invention
The invention relates to an improved ink jet printhead, and more particularly to a process for sealing a manifold to a printhead die and to a thermal ink jet printhead with sealed manifold and printhead die.
2. Description of Related Art
A thermal ink jet printhead is a device which ejects fluid (ink) in a controllable fashion by means of electrical pulses passed through resistive heating elements which are in thermal contact with the ink. Ink from a reservoir travels through a manifold located above a printhead die and into the printhead die through an ink inlet. The printhead die consists of a channel plate in which fluidic pathways are formed for example by etching, bonded on top of a heater plate. The heater plate may contain heating elements, leads and preferably some addressing electrodes to reduce required interconnection density. Insofar as possible, the microelectric packaging of the printhead die follows IC and hybrid industry standard methods such as epoxy die bonding of the silicon device onto the substrate, as well as wire bonding to accomplish electrical interconnection. However, the fluid handling requirements of the printhead give rise to additional packaging requirements.
As part of the printhead, a manifold is mounted to a substrate having an interconnection board and the printhead die is mounted on a heater plate situated in the substrate. The manifold has an inlet and the manifold is positioned over the printhead die so that the inlet is contiguous with a corresponding inlet in the die to form a continuous passageway. The manifold provides an ink supply through the inlets to the printhead die. Hence, the ink inlet of the thermal ink jet die must be sealingly positioned against and coincident with the ink inlet of the manifold. A tight seal has required applying seal bead completely around the inlet orifice of the die prior to positioning of the manifold.
The printhead die is diced from a silicon wafer which has been etched with elongated slots. Hawkins, U.S. Pat. No. 4,935,750 describes a method for producing the die from a wafer and the description of this patent is incorporated herein by reference. Downsizing of the printhead die is desirable because as the area of the die is decreased, the die may be manufactured more quickly and more dies may be manufactured per wafer of stock material. A limiting factor to reducing the area of the printhead die is that a sufficient area is required around the inlet for the purpose of supporting sealant to provide an adequate seal to the orifice of the manifold inlet.